1. Field of the Invention
The present invention relates to the printing of labels and more specifically to the printing and encoding of labels containing radio frequency identification (RFID) technology, herein referred to as smart labels.
2. Description of Related Art
The automatic identification industry has undergone many recent developments with respect to the use of transponders to track and identify objects. RFID systems are well known in the art, and the basic RFID system consists of an antenna, a transceiver, and a transponder (RFID tag). The RFID tag is encoded with information for easy retrieval. The antenna emits radio signals to activate the RFID tag so that the tag can be read, and acts as a conduit between the tag and the transceiver. When the antenna is packaged with the transceiver, an interrogator is created. The interrogator is used to read the information from the RFID tag when necessary. The interrogator emits radio waves in various ranges, depending upon the power output of the interrogator as well as the range of the RFID tag. When an RFID tag passes through the electromagnetic zone, it detects the interrogator's activation signal through an antenna in the RFID tag. The antenna senses the interrogating field and acts as the method of transmitting a response to interrogation. The interrogator receives and decodes the data encoded in the RFID tag's integrated circuit and the data is passed to a host computer for processing.
A so-called smart label is a development from RFID systems that incorporates an integrated circuit coupled to an antenna with read/write capability used to store data for identification and tracking of articles. The resulting RFID tag is small enough to be placed into a standard adhesive label without appreciably affecting the thickness of the label. Thus, the smart label can be used in many applications such as express parcel delivery, airline baggage handling and security verification. The smart label offers advantages over standard labels by providing the ability to rewrite data into the label, read the label without line-of-sight restriction, and longer read range.
Conventional prior art label printers are capable of printing labels in a fast, efficient way. However, with the development of smart labels, there exists a need for label printers that can not only print visible indicia such as bar code symbols, addresses, logos, etc., but that also have the capability to read and write to RFID tags. Optimally, the interrogating functions would be carried out in the same time frame as the exterior printing of the label. Unfortunately, no prior art printer has effectively been able to accomplish this.
Prior art label printers generally comprise thermal printers, which use a thermal printing head for the transfer of indicia to the labels. The thermal print head is generally connected electronically to a computer processor by way of a control circuit. The thermal print head includes at least one electrically-resistive thermal print element that is maintained in contact against an opposing pressure member, with the thermal print element being capable of producing heat upon the application of an electronic signal thereto. A thermal print medium, such as a specially-coated paper in sheet or strip form, is interposed between the thermal print head and the pressure member, whereby the pressure member maintains the thermal print medium in contact with the thermal print element. When the thermal print medium is at ambient temperature, the coating is inactive; however, when the temperature of the thermal print medium is raised to or above a certain threshold temperature, the coating undergoes a chemical reaction and is exposed. Thus, when an electrical signal is applied to the thermal print element, the heat produced thereby raises the temperature of the thermal print medium above a threshold temperature so as to expose at least a portion of the coating, whereby a character or a portion of a character is printed. Thermal printers have many inherent advantages over other types of printers including the production of clearly printed images at high output rates, quiet and clean operation, and relatively small size.
Prototype printers that attempt to combine thermal printing technology with RFID interrogating technology are deficient in that the write time to the RFID tag takes substantially longer than the printing time to the label.
It is therefore an object of this invention to provide a method and apparatus to increase the speed required to program the RFID tag portion of a smart label.
It is a further object of this invention to provide a method and apparatus to increase the speed of the interrogating portion of a smart label relative to the exterior printing speed of the smart label so that the two functions are completed in a similar time frame.
It is still a further object of this invention to provide a method and apparatus to increase the overall throughput speed of a smart label.